RETENTION OF MOLYBDENUM(VI) BY 3 FINNISH MINERAL SOILS

Retention of molybdate by three Finnish mineral soils from 10(-4) and 10(-5) M sodium molybdate solutions at room temperature was investigat ed at pH 2.3-7.5. In the adsorption experiments 0.02 M KCl was used as ionic medium, and the samples were left to equilibrate for 72 h. The solid:solution ratio was 1:100 (w:v). Maximum adsorption occurred belo w pH 4.5, where about 60-80 % of added molybdenum was retained. Desorp tion of the adsorbed molybdenum was measured by adding 50 ml of 0.02 M KCl into weighed soil samples and shaking for 17 h in an apparatus wi th a mechanical stirrer. In each soil an appreciable amount of Mo was so tightly bound that it could not be removed by KCl treatment.